Silence cancel urb errors during iso stream cancel

When cancelling an active iso stream some iso packets will likely complete
while we are cancelling, but we will see them as uncomplete as long as we've
not asked libusb to check for complete transfers, this is inherently racy and
there is nothing we can do. Thus we will sometimes try to cancel already
completed transfers which will fail.

This is not a problem, but libusb spews ugly error messages to stderr when
this happens. This patch silences these error messages.

3 files changed, 14 insertions, 3 deletions

diff --git a/usbredirhost/usbredirhost.c b/usbredirhost/usbredirhost.c
index 5985c9e..d348ef0 100644
--- a/usbredirhost/usbredirhost.c
+++ b/usbredirhost/usbredirhost.c
@@ -75,6 +75,7 @@ struct usbredirhost {
     usbredirparser_write write_func;
     void *func_priv;
     int verbose;
+    libusb_context *ctx;
     libusb_device *dev;
     libusb_device_handle *handle;
     struct libusb_config_descriptor *config;
@@ -374,7 +375,9 @@ static int usbredirhost_release(struct usbredirhost *host)
     return ret;
 }
 
-struct usbredirhost *usbredirhost_open(libusb_device_handle *usb_dev_handle,
+struct usbredirhost *usbredirhost_open(
+    libusb_context *usb_ctx,
+    libusb_device_handle *usb_dev_handle,
     usbredirparser_log log_func,
     usbredirparser_read  read_guest_data_func,
     usbredirparser_write write_guest_data_func,
@@ -392,6 +395,7 @@ struct usbredirhost *usbredirhost_open(libusb_device_handle *usb_dev_handle,
         return NULL;
     }
 
+    host->ctx = usb_ctx;
     host->dev = libusb_get_device(usb_dev_handle);
     host->handle = usb_dev_handle;
     host->log_func = log_func;
@@ -893,6 +897,10 @@ static void usbredirhost_cancel_iso_stream(struct usbredirhost *host,
     int i;
     struct usbredirtransfer *transfer;
 
+    /* This is inherently racy, some of the transfers we consider in flight
+       may have already completed, suppress libusb cancel error messages. */
+    libusb_set_debug(host->ctx, 0);
+
     for (i = 0; i < host->endpoint[EP2I(ep)].iso_transfer_count; i++) {
         transfer = host->endpoint[EP2I(ep)].iso_transfer[i];
         if (transfer->iso_packet_idx == ISO_SUBMITTED_IDX) {
@@ -922,6 +930,7 @@ static void usbredirhost_cancel_iso_stream(struct usbredirhost *host,
         host->endpoint[EP2I(ep)].iso_pkts_per_transfer = 0;
         host->endpoint[EP2I(ep)].iso_transfer_count = 0;
     }
+    libusb_set_debug(host->ctx, host->verbose);
 }
 
 /**************************************************************************/
diff --git a/usbredirhost/usbredirhost.h b/usbredirhost/usbredirhost.h
index 6644311..a98072c 100644
--- a/usbredirhost/usbredirhost.h
+++ b/usbredirhost/usbredirhost.h
@@ -49,7 +49,9 @@ struct usbredirhost;
       thread has its own libusb_context. IOW usbredirhost does not use
       static or global variables.
 */
-struct usbredirhost *usbredirhost_open(libusb_device_handle *usb_dev_handle,
+struct usbredirhost *usbredirhost_open(
+    libusb_context *usb_ctx,
+    libusb_device_handle *usb_dev_handle,
     usbredirparser_log log_func,
     usbredirparser_read  read_guest_data_func,
     usbredirparser_write write_guest_data_func,
diff --git a/usbredirserver/usbredirserver.c b/usbredirserver/usbredirserver.c
index 67a9bf0..2733748 100644
--- a/usbredirserver/usbredirserver.c
+++ b/usbredirserver/usbredirserver.c
@@ -333,7 +333,7 @@ int main(int argc, char *argv[])
             continue;
         }
 
-        host = usbredirhost_open(handle, usbredirserver_log,
+        host = usbredirhost_open(ctx, handle, usbredirserver_log,
                                  usbredirserver_read, usbredirserver_write,
                                  NULL, VERSION, verbose);
         if (!host)